May 28, 2014

Taste Receptor Gene Determines How Well We Sense Food

Some people’s sense of taste is so perceptive, they have a strong dislike for food that a majority of people enjoy, such as spicy foods or ‘hoppy’ beers.

According to a new report published in the journal Frontiers in Integrative Neuroscience, these so-called supertasters get their increased sensitivity from a variation in the taste receptor gene TAS2R38 – not a higher than normal amount of taste buds as had been previously thought.

"There is a long-held belief that if you stick out your tongue and look at the bumps on it, then you can predict how sensitive you are to strong tastes like bitterness in vegetables and strong sensations like spiciness," said study author Nicole Garneau, head of the Department of Health Sciences at the Denver Museum of Nature & Science. "The commonly accepted theory has been that the more bumps you have, the more taste buds you have and therefore the more sensitive you are."

For the study, the authors had more than 3000 volunteers visiting the Denver museum's Genetics of Taste Lab stick their tongue out so that their taste buds could be counted. Volunteers also had their sensitivity to bitter-tasting compounds phenylthiocarbamide and propylthiouracil measured. Out of this initial group – only 394 subjects were included in the final analysis.

Study researchers then took cell swabs from this smaller group of volunteers to determine their DNA sequence at the known location for TAS2R38. Results of a genetic analysis showed that some variations in the TAS2R38 gene make it more probable that somebody is hypersensitive to bitter compounds. The researchers also found that the number of taste buds on the tongue, also known as papillae, does not reflect higher taste sensitivity.

"No matter how we looked at the data, we couldn't replicate this long held assumption that a high number of papillae equals supertasting," Garneau said.

The study authors noted that some of their work was done with the help of over 130 volunteer citizen scientists who had been specially trained by Garneau and her colleagues. The study authors also called the term ‘supertaster’ antiquated and suggested using the more objective ‘hypergeusia’ instead.

"What we know and understand about how our bodies work improves greatly when we challenge central dogmas of our knowledge,” Garneau said. “This is the nature of science itself.”

“As techniques improve, so too does our ability to do science, and we find that what we accepted as truth 20, 30, or 100 years ago gets replaced with better theories as we gather new data, which advances science,” she added. “In this case, we've proven that with the 'Denver Papillae Protocol', our new method for objective analysis for papillae density, we were unable to replicate well-known studies about supertasting."

A refined sense of taste can be very valuable – in fact, Britain’s Costa Coffee announced in 2009 that the company had taken out an insurance policy on one of their taste tester’s tongue worth $14 million.

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Image 2 (below): Citizen scientists in the Genetics of Taste Lab enroll Museum guests in the research study. Guests answer questions about themselves and mark their age and gender on the “Where Do You Fit” data tracking wall. The lab is located as a specialized learning area of Expedition Health, the Museum’s permanent health exhibition shown in the background. Credit: Denver Museum of Nature & Science.